Fat products of the above kind, such as low calorie spreads, wrapper and tub margarines have to comply with various requirements as regards taste, thermal stability, cycle stability, spreadability, melting behaviour and the like.
More in particular for fat products, such as those containing large amounts of polyunsaturated components, or having increased softness at refrigerator temperature, it can be difficult to comply with the requirements for cycle and thermal stability, as well as with those for cycle stability.
Stability against temperature changes (cycle-stability) is important in view of the possible temperature changes during transport and storage, but also in view of household use where frequent temperature changes can occur. Improved storage temperature cycle stability is therefore advantageous.
Heat stability, i.e. the absence of phase separation and of oil exudation at a certain temperature determines the ambient temperatures at which the product can be used. It is, of course, clear that, with respect to the heat stability, in tropical areas other temperature requirements are set than in for example the arctic region.
In general the heat stability is governed by the amount of hardstock, i.e. highmelting fats. A better heat stability, however, normally leads to a deterioration of the oral response, especially after temperature cycling. This is because the oral response largely depends on the melting behaviour of the fat phase.
Although Applicants do not wish to be bound by theory, it is believed that on the one hand the heat stability and on the other hand oral response and cycling stability do not well go together because the requirement of heat stability (e.g. heat stability at 30.degree. C. for 24 hours) normally leads to the formulation of fat blends containing relatively high amounts of higher melting triglycerides, having a melting point above mouth temperature. These higher melting triglycerides are believed to be responsible for the deterioration of oral response and the reduced cycling stability.
In most conventional fat products, shortly after production, the higher melting triglycerides are crystallized in mixed crystals of a non-equilibrium composition, having incorporated therein considerable amounts of the lower melting triglycerides. In a well formulated blend the melting point of the mixed crystals is just below mouth temperature. In the mouth a fat product, containing such a blend, will melt entirely, whereby, since the water-in-oil emulsion is no longer stabilized, the aqueous phase together with the salt and flavour compounds present therein are released.
However, when conventional fat products are subjected to temperature cycling, the mixed crystals demix, and a separate, more pure fraction of the higher melting triglycerides crystallizes, partially in the form of shells, surrounding and stabilizing water droplets. In the mouth these water droplets remain stabilized by these high melting fat crystals, and consequently the flavour compounds dissolved therein will not be released. Conventional products displaying good heat stability always combine this property with a rather bad cycling stability and oral response. Vice versa, conventional products having improved cycle stability, due to the presence of a relatively small amount of high melting triglycerides, always suffer from a poor heat stability.
In this application, by fat is meant, unless indicated otherwise, an edible substance, which may be solid or liquid at ambient temperature, consisting essentially of triglycerides such as, for example, soybean oil, sunflower oil, palm oil, coconut oil, fish oil, lard and tallow, which may have been partially or completely hydrogenated or modified otherwise, or comprising non-toxic material having properties similar to triglycerides, which material may be indigestible, such as for example waxes, e.g. jojoba oil and hydrogenated jojoba oil, and poly fatty acid esters of mono- and disaccharides, e.g. sucrose octa fatty acid ester, or mixtures thereof. The terms fat and oil, moreover, are used interchangeably.
European Patent Application 130642 describes a method for making a fat spread on the basis of fractionated palm oil and/or palm stearin, which results in a spread having a double peaked differential scanning calorimetry curve. This method essentially comprises stepwise crystallization of the fat, resulting in a DSC-peak between 10.degree. C. and 25.degree. C. and a peak between -10.degree. C. and 5.degree. C.
It is an object of the present invention to provide an edible fat containing fat product comprising a improved process for preparing continuous fat phase, and an aqueous phase dispersed in said fat phase, which process provides a product that has an improved pattern of properties, especially as regards thermal stability, oral response and storage temperature cycle stability.